[ARM] Add missing return to ARMTTIImpl::isLoweredToCall.

[craig.topper]

Summary

I assume we meant to return the result of the call to
BaseT::isLoweredToCall(F).

This might not be a functional change in practice because it would
still hit the default case in the switch and call
BaseT::isLoweredToCall(F) at the end.

[efriedma]

LGTM

llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp

ARMTTIImpl::getIntrinsicInstrCost(const IntrinsicCostAttributes &ICA,
   }
   }
 
   return BaseT::getIntrinsicInstrCost(ICA, CostKind);
 }
 
 bool ARMTTIImpl::isLoweredToCall(const Function *F) {
   if (!F->isIntrinsic())
-    BaseT::isLoweredToCall(F);
+    return BaseT::isLoweredToCall(F);
 
   // Assume all Arm-specific intrinsics map to an instruction.
   if (F->getName().startswith("llvm.arm"))
     return false;
 
   switch (F->getIntrinsicID()) {
   default: break;
   case Intrinsic::powi: